In millimeter wave radar systems (e.g., as for automotive safety and comfort applications) antenna structures are placed on high frequency substrates or high frequency printed circuit boards (HF PCBs), increasing the overall cost of design due to the extra high expense of such high frequency substrates. Antennas such as microstrip antennas (e.g., patch antennas) are often built on these special high frequency substrates. HF PCBs are often constructively based on Rogers, Taconic or other PTFE materials.
Millimeter wave output power can be generated on a semiconductor monolithic microwave integrated circuit (MMIC), which may be located also on the HF PCB. MMIC devices typically perform functions such as microwave mixing, power amplification, low noise amplification, and high frequency switching. The inputs and outputs on MMIC devices frequently match to a characteristic impedance (e.g., 50 ohms) and interconnect to an antenna. These interconnections between MMIC devices and an antenna generally involve a lossy chip/board interface (e.g., bond wires).
Whenever a source of power, such as MMIC devices, delivers power to a load, the power is delivered most efficiently when the impedance of the load is equal to or matches the complex conjugate of the impedance of the source (impedance matching). For two impedances to be complex conjugates, their resistances are equal, and their reactance are equal in magnitude but of opposite signs. Such impedance matching between antennas and chip output can suffer from large manufacturing tolerances of the bonding process and on printed circuit board (PCB) wiring.
Because of a large demand for efficient, less expensive, and cost-effective radar sensing, suppliers face the challenge of delivering antenna packages with maximum potential range, data rate and power integrated in the same radar system.